Process for dewaxing hydrocarbon oils



Dec. 19,'1933. E. PETTY PROCESS FOR DEWAXING HYDHOCRBON OILSk Filed July 27, 1932 mw QSSQ Patented Dec. 19, 1933 UNITED STATES PATENT OFFICE Earl Petty, New York, N. Y., assignor to Alco Products, Incorporated, New York, N. Y., a corporation of Delaware Application July 27, 1932. Serial No. 624,968

5 Claims. (Cl. 196-19) My invention relates to a process for dewaxing hydrocarbon oils and more particularly to a process of dewaxing in which pressable wax crystals are produced from crude oils by chillins. I

Heretofore, to produce pressable wax distillates from crude oil it required a high degree of l fractionation and a very careful selection of the pressing fraction. This pressing fraction usual- 1y had a boiling rangefrom 450 F. to 675 F.

-One object of my invention is to provide a method of dewaxing hydrocarbon oils in which the fraction which canbe dewaxed by pressing isY amplified to include oils of a boiling range up to 725 F. to 750 F. Y

Another object of my invention is to provide amethod of chilling hydrocarbon oils which will greatly increase the formation of pressable wax therein.

Other and further objects of my invention will appear from the following description.

'I'he accompanying figure, which is to be read in conjunction with the instant specification and which forms part thereof, shows a diagrammatic view of an apparatus capable of carrying out my invention.

In general, my invention consists in blending under pressure a predetermined amount oi' propane with the wax bearing oil. It is to be understood that throughout this specincation by "propane" is meant any of the low boiling hydrocarbons which may exist in a liquid state in the normal temperature range by"y the imposition of super atmospheric pressures. Propane, for example, is liquidl within the normal temperature range at pressures between 80 to 120 pounds per square inch. At atmospheric pressure it boils at F. and solidiiles at about -300 F. It is a solvent for both the wax and the oil at normal temperatures.

In my co-pending application 632,278 for a Process of crystallization of wax,.I point out the undesirability of having an excess of propane, in that .wax crystallization is retarded. In the instant application I propose, as pointed out above, to use a predetermined amount of propane. By predetermined amount" I mean an amount insumcient to chill the oil to the deaired low temperature solely by evaporation of the propane. By using a predetermined amount of propane, an excess of diluent is avoided, thus permitting a favorable crystal growth.

The blended mixture still under pressure is passed through pre-coolers in order to chill the same by heat exchange. The mixture is .scraped surface heat exchangers.

then passed to an evaporator in which the pressure is reduced to permit the evaporation of the propane, during which evaporation further chilling is effected. The effect of the propane upon the wax during the pre-cooling and the nal chilling is such that a desirable wax crystal capable of being ilteredis produced. This eifect enables me by the practice of my process to extend the range of pressable wax bearing oils. The propane is recovered from the evaporator for re-use. The chilled oil containing wax crystals is then passed to a iilter press.

The lter press room is kept in an atmosphere of inert vapor which will not support combustion, to preclude the danger of fire from the evaporation of propane while the wax is being pressed; The oil which is recovered from the pressing opration and which is at a very low temperature is passed in heat exchange with the incoming mixture and is used as the cooling medium, although it is to be understood that any other suitable refrigerant may be employed. 'I'he oil is then passed to a pressure evaporator to insure the complete removal of propane therefrom, and finally stripped by steam to remove the last trace of any of the volatile products, and then passed to storage.

More particularly, referring now to the drawing, the distillate to be dewaxed is pumped from storage tank 1 by pump 2 .through valved line 3 into blending tank 4. Propane, under pressure and in liquid form, is pumpedfrom tank 5 through line 6 by pump 7 into line 8 which enters the blending tank 4, in which a thorough mixture of the oil to be dewaxed and the propane is eiected. It is to be understood that suitable agitating means may be provided in `the blending tank. The mixture or solution is pumped through valved line -9 by pump 10, through heat exchangers 11. These heat exchangers may be -of any suitable type. 'I'he drawing illustrates a diagrammatic view of the The solution is chilled in heat exchangers 11 and passes through line 12 into evaporator 13, in which the` pressure is reduced to allow the propane vto evaporate to secure additional and further chilling. I f desired, propane may be passed through line 14 and Dumped by pump 15 through line 16 into the evaporator to secure additional and further cooling.

The gaseous propane leaves the evaporator 13 through line 17 and may be recovered by any suitable means. Separator 18 is provided to insure that no oil is carried out of the system, the

oil returning through line 19. Pump 15 is adapted to take suction through valve line 20 for recirculation of the solution. Chilled oil containing pressable wax crystals leaves evaporator 13 through valved line 21 and passes into a plurality of filter presses 22, 23 and 24 which are arranged in parallel. The filter presses are located in a press chamber 25 which is gas tight. Into the press room 25 an inert gas, such as carbon dioxide, is introduced through line 26. The inert gas forms the atmosphere of the press room and prevents the danger of nre due to the presence of propane gas escaping from the solution being dewaxed. The inert gas leaves the press room through line 27.

The wax leaves the filter presses through lines 28, 29 and 30 and passes into wax receiver 31 which is provided with a fitting 32 through which a reduced pressure may be placed upon the wax receiver to evaporate therefrom all traces of volatile propane. The dewaxed oil leaves the filter presses through lines 32, 33 and 34 through line 35, and is pumped by pump 36 through the heat exchangers 11 to chill the incoming solution. The oil leaves the heat exchangers 11 through line 37 and passes into pressure evaporator 38 in which the remaining propane-solvent is removed and recovered overhead through line 39, passing through condenser 40 into receiver 41. A recirculating line 42 is provided to insure the complete removal of oil from the head product. The tail product is withdrawn through line 43 and passed into reboiler 44 whence it may be recirculated through line 45 or passed into stream stripper 46 through line 47. The dewaxed oil freed of the solvent is then pumped by pump 48 into storage tank 49.

The filter presses may be of the conventional type or may be special centrifuges or batch type filters.

It will be seen that I have accomplished the objects of my invention. I am enable to produce pressable wax from distillates of a greater boiling range. By my method of chilling, I am enable to produce pressable wax where it has been impossible heretofore to do so, and also toy produce a greater amount of pressable wax for a given fraction, enabling the complete dewaxing thereof. An increased crystal formation is achieved by the use of propane' as a diluent accompanied by the manner in which I chill the solution. I preclude the danger of re in the press room by keeping it in an atmosphere of inert gas.

It will be understood that certain features, sub-combinations and operations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is, therefore, to be understood that my. invention is not to be limited to the specific details shown and described.

Having thus described my invention, what I claim is:

1. In a method of dewaxing hydrocarbon oils, the steps which include diluting the oil to be dewaxed with an amount of liqueed normally gaseous diluent-refrigerant insuilicient to chill the oil to the desired low temperature solely by the evaporation of the diluent-refrigerant at atmospheric pressure, reducing the temperature of the diluted oil by heat exchange with an extraneous cold medium to a temperature above the said desired low temperature, thereafter further reducing the temperature to the desired extent by reducing the concentration of the diluent-refrigerant whereby the wax is thrown out of solution in readily lterable form and thereafter filtering 01T the wax from the remaining solution.

2. In a method of dewaxing hydrocarbon oils, including hydrocarbon oils having fractions boiling above 675 F., the. steps which include diluting the oil to be dewaxed with an amount of liquefied normally gaseous diluent-refrigerant insufcient to chill the oil to the desired low temperature solely by the evaporation of the diluent-refrigerant at atmospheric pressure, reducing the temperature of the diluted oil by heat exchange with an extraneous cold medium to a temperature above the said desired low temperature, thereafter further reducing the temperature to the desired extent by reducing the concentration of the diluent-refrigerant whereby the wax is thrown out of solution in readily lterable form and thereafter filtering off the wax from the remaining solution.

3. The process as in claim 1 wherein the extraneous refrigerant medium for the indirect heat exchange cooling step is the dewaxed chilled oil. n

4. 'Ihe process as in claim 1 wherein the flltering step is carried on in an inert atmosphere.

5. A method of dewaxing hydrocarbon oils as in claim 1 wherein the concentration of the di- I final chilling step will be present in sufficient 1.)'

quantity to permit favorable wax crystal growth.

EARL PE'I'I'Y. 

